The invention relates to speed measurement for an electrical permanent-magnet synchronous machine. The invention relates in particular to a speed measurement device which is provided for this purpose, to a primary part of a permanent-magnet electrical synchronous machine, and to a method for measurement of the speed.
By way of example, absolute rotation transmitters are speed measurement devices for electrical machines. In the case of linear motors, by way of example, length measurement systems can be used for speed measurement. Devices such as these for measurement of a speed of an electrical rotating machine or of an electrical linear machine are complex to manufacture, and are costly to produce.
For speed-regulated or rotation-speed-regulated operation of permanent-magnet synchronous machines from a converter, it is necessary to know the absolute rotor position as well as the actual speed or rotation speed. In general, an external tachogenerator or a position transmitter, from which the rotation speed signal can be differentiated, is required for this purpose.
In the case of linear motors, a speed value for a linear movement is required instead of the rotation speed signal as the speed signal. In order to obtain a speed signal, which is required for control of the electrical machine, in particular of the permanent-magnet electrical synchronous machine, from a position signal, the position signal must be differentiated. The position signal must have high resolution for this purpose. This involves a high degree of complexity, irrespective of whether the position signal relates to a position with respect to a rotary movement or a linear movement. Particularly for linear motors and hollow-shaft motors, such as torque motors, such signal determination requires tachogenerators that are suitable for this purpose, and thus a high degree of complexity.
U.S. Pat. No. 4,710,683 discloses a device for identification of a rotary movement. A ring structure is used for movement identification, which has magnets arranged in a circular shape and is coupled to a rotary electrical machine. Furthermore, two sensors are used for movement identification and are influenced by the magnetic field of the magnets arranged in a circular shape, with Hall sensors or inductively acting sensors being used as sensors. The sensors detect the free-space field of the magnets. This is a stray field, so that the measurement by means of the sensors loses accuracy.